The present invention relates to a numeric operation processor for providing various numeric operation functions, and more particularly to a floating point operation processor suitable for floating point addition, subtraction, multiplication and division and transcendental entire function operation.
"NIKKEI ELECTRONICS", July 14, 1986, No. 399, pages 171-185, published by Nikkei McGrow Hill (original English version thereof was published in "EDN", Jan. 9, 1986, by Cahners Publishing Corp. U.S.A.) shows a floating point operation processor having a high speed operation unit, a microsequencer (microprogram sequence controller), a register file and a data ROM (read-only memory). As shown in pages 179-185, a function operation uses a convergence equation for the function operation or an approximate equation by a series polynomial such as a Chebyshev approximation polynomial. The data ROM is a constant ROM of a small storage capacity for storing constants of the convergence equation or series polynomial for approximation.
Since this processor has only a small capacity constant data ROM, when a transcendental entire function is to be calculated, a classic series polynomial is iteratively operated on for an appropriate number of terms starting from an initial value to obtain a solution. In this case, coefficients of the series polynomial are stored in the constant data ROM. Basic operations to solve the function with a sufficient accuracy, that is, addition and multiplication require a large number of times of iteration of operation, and the execution time of the function operation is very long relative to the execution time of the basic operations. For example, in the above example, the number of steps of operation is several tens of steps and the function operation time of 3-10 microseconds is required even if the fastest ALU (arithmetic and logic unit) and multiplier (operation time: 100-150 ns) which are currently available as VLSI (very large scale integrated) devices are used. Accordingly, even if an existing expensive high speed operation coprocessor for a microprocessor is used, the cost-performance (performance/cost) attained in the addition, subtraction, and multiplication operations is not attainable in the function operation.